Risk-based Authentication
Risk-based authentication allows CAS to detect suspicious and seemingly-fraudulent authentication requests based on past user behavior and collected authentication events, statistics, etc. Once and after primary authentication where the principal is identified, the authentication transaction is analyzed via a number of configurable criteria and fences to determine how risky the attempt may be. The result of the evaluation step is a cumulative risk score that is then weighed against a risk threshold set by the CAS operator. In the event that the authentication attempt is considered risky well beyond the risk threshold, CAS may be allowed to take action and mitigate that risk.
In summary, the story told is:
If an authentication request is at least [X%] risky, take action to mitigate that risk.
The functionality of this feature is ENTIRELY dependent upon collected statistics and authentication events in the past. Without data, there is nothing to analyze and no risk to detect.
Note that evaluation of attempts and mitigation of risks are all recorded in the audit log.
If you need to preemptively evaluate authentication attempts based on various characteristics of the request, you may be interested in this guide instead.
Risk Calculation
One or more risk calculators may be enabled to allow an analysis of authentication requests.
A high-level explanation of the risk calculation strategy follows:
- If there is no recorded event at all present for the principal, consider the request suspicious.
- If the number of recorded events for the principal based on the active criteria matches the total number of events, consider the request safe.
IP Address
This calculator looks into past authentication events that match the client ip address. It is applicable if you wish to consider authentication requests from unknown ip addresses suspicious for the user. The story here is:
Find all past authentication events that match the current client ip address and calculate an averaged score.
Browser User Agent
This calculator looks into past authentication events that match the client’s user-agent string. It is applicable if you wish
to consider authentication requests from unknown browsers suspicious for the user. The story here is:
Find all past authentication events that match the current client browser and calculate an averaged score.
Geolocation
This calculator looks into past authentication events that contain geolocation data, and compares those with the current geolocation. If current geolocation data is unavailable, it will attempt to geocode the location based on the current client ip address. This feature mostly depends on whether or not geodata is made available to CAS via the client browser and requires geotracking of authentication requests.
The story here is:
Find all past authentication events that match the current client location and calculate an average score.
Date/Time
This calculator looks into past authentication events that fit within the defined time-window. It is applicable if you wish to consider authentication requests outside that window suspicious for the user. The story here is:
Find all past authentication events that are established X hours before/after now and calculate an averaged score.
Risk Mitigation
Once an authentication attempt is deemed risky, a contingency plan may be enabled to mitigate risk. If configured and allowed, CAS may notify both the principal and deployer via both email and sms.
Block Authentication
Prevent the authentication flow to proceed and disallow the establishment of the SSO session.
Multifactor Authentication
Force the authentication event into a multifactor flow of choice, identified by the provider id.
Configuration
Support is enabled by including the following dependency in the overlay:
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<dependency>
<groupId>org.apereo.cas</groupId>
<artifactId>cas-server-support-electrofence</artifactId>
<version>${cas.version}</version>
</dependency>
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implementation "org.apereo.cas:cas-server-support-electrofence:${project.'cas.version'}"
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dependencyManagement {
imports {
mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
}
}
dependencies {
implementation "org.apereo.cas:cas-server-support-electrofence"
}
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dependencies {
/*
The following platform references should be included automatically and are listed here for reference only.
implementation enforcedPlatform("org.apereo.cas:cas-server-support-bom:${project.'cas.version'}")
implementation platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES)
*/
implementation "org.apereo.cas:cas-server-support-electrofence"
}
The following settings and properties are available from the CAS configuration catalog:
cas.authn.adaptive.policy.require-timed-multifactor[0].provider-id=
The mfa provider id that should be triggered.
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cas.authn.adaptive.policy.reject-browsers=
Comma-separated list of strings representing browser user agents to be rejected from participating in authentication transactions.
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cas.authn.adaptive.policy.reject-countries=
Comma-separated list of strings representing countries to be rejected from participating in authentication transactions.
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cas.authn.adaptive.policy.reject-ip-addresses=
Comma-separated list of strings representing IP addresses to be rejected from participating in authentication transactions.
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cas.authn.adaptive.policy.require-multifactor=
A map of (
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cas.authn.adaptive.policy.require-timed-multifactor=
This property binds a valid mfa provider to a collection of rules that deal with triggering mfa based on that provider based on properties of date/time. One may want to force mfa during weekends, after hours, etc and the ruleset provides a modest configuration set where time can also be treated as trigger.
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cas.authn.adaptive.policy.require-timed-multifactor[0].on-days=
Trigger mfa on the following days of the week.
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cas.authn.adaptive.policy.require-timed-multifactor[0].on-or-after-hour=20
Trigger mfa after this hour, specified in 24-hour format.
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cas.authn.adaptive.policy.require-timed-multifactor[0].on-or-before-hour=7
Trigger mfa before this hour, specified in 24-hour format.
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Configuration Metadata
The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.
Be Selective
This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.
YAGNI
Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.
Naming Convention
Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all
forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where
this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those
that might be presented to the system via an external library or framework such as Spring Boot, etc.
When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.
The only possible exception to this rule is when naming actuator endpoints; The name of the
actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.
Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided
to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with
the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition
or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the
way you intend.
Validation
Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be
recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system
property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled
via Configuration Metadata and property migrations applied automatically on
startup by Spring Boot and family.
Indexed Settings
CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be
incremented by the adopter to allow for distinct multiple configuration blocks.
Messaging & Notifications
The following settings and properties are available from the CAS configuration catalog:
cas.authn.adaptive.risk.response.mail.attribute-name=mail
Principal attribute name that indicates the destination email address for this message. The attribute must already be resolved and available to the CAS principal.
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cas.authn.adaptive.risk.response.mail.from=
Email from address.
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cas.authn.adaptive.risk.response.mail.subject=
Email subject line. The subject can either be defined verbaitm, or it may point to a message key in the language bundle using the syntax#{subject-language-key}. This key should point to a valid message defined in the appropriate language bundle that is then picked up via the active locale. In case where the language code cannot resolve the real subject, a default subject value would be used.
This setting supports the Spring Expression Language.
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cas.authn.adaptive.risk.response.sms.attribute-name=phone
Principal attribute name that indicates the destination phone number for this SMS message. The attribute must already be resolved and available to the CAS principal.
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cas.authn.adaptive.risk.response.sms.from=
The from address for the message.
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cas.authn.adaptive.risk.response.sms.text=
The body of the SMS message.
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cas.authn.adaptive.risk.response.mail.bcc=
Email BCC address, if any.
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cas.authn.adaptive.risk.response.mail.cc=
Email CC address, if any.
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cas.authn.adaptive.risk.response.mail.html=false
Indicate whether the message body should be evaluated as HTML text.
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cas.authn.adaptive.risk.response.mail.priority=1
Set the priority (
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cas.authn.adaptive.risk.response.mail.reply-to=
Email Reply-To address, if any.
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cas.authn.adaptive.risk.response.mail.text=
Email message body. Could be plain text or a reference to an external file that would serve as a template. If specified as a path to an external file with an extension.gtemplate, then the email message body would be processed using the Groovy template engine. The template engine uses JSP style <% %> script and <%= %> expression syntax or GString style expressions. The variable out is bound to the writer that the template is being written to. If using plain text, the contents are processed for string subtitution candidates using named variables. For example, you may refer to an expected url variable in the email text via ${url}, or use ${token} to locate the token variable. In certain cases, additional parameters are passed to the email body processor that might include authentication and/or principal attributes, the available locale, client http information, etc.
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cas.authn.adaptive.risk.response.mail.validate-addresses=false
Set whether to validate all addresses which get passed to this helper.
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The following settings may also need to be defined to describe the mail server settings:
spring.mail.default-encoding=UTF-8
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spring.mail.host=
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spring.mail.jndi-name=
Session JNDI name. When set, takes precedence over other Session settings. How can I configure this property?
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spring.mail.password=
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spring.mail.port=
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spring.mail.properties=
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spring.mail.protocol=smtp
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spring.mail.test-connection=false
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spring.mail.username=
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Configuration Metadata
The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.
Be Selective
This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.
YAGNI
Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.
Naming Convention
Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all
forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where
this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those
that might be presented to the system via an external library or framework such as Spring Boot, etc.
When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.
The only possible exception to this rule is when naming actuator endpoints; The name of the
actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.
Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided
to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with
the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition
or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the
way you intend.
Validation
Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be
recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system
property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled
via Configuration Metadata and property migrations applied automatically on
startup by Spring Boot and family.
Indexed Settings
CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be
incremented by the adopter to allow for distinct multiple configuration blocks.
To learn more about available options, please see this guide or this guide.
Remember
- You MUST allow and configure CAS to track and record authentication events.
- You MUST allow and configure CAS to geolocate authentication requests.
- If the selected contingency plan is to force the user into a multifactor authentication flow, you then MUST configure CAS for multifactor authentication and the relevant provider.